Kinetics and Mechanism on a Reaction of Allyl Radical with Ethylene

Abstract

First-order reaction kinetics fitted the rate of 1,5-hexadiene decomposition and the rate constant obtained was k=1012.9 exp (-55,000/RT) sec-1, which indicated that allyl radical generated was effectively quenched by ethylene. The main primary products were cyclopentene (38.0mol%), 1 pentene (28.5), 1-butene+butadiene (19.0) and propylene (14.5).Minor ones were 1,4 pentadiene and cyclopentadiene. A mechanism was proposed focussing the discussion on C5 products formation from allyl radical and ethylene.

Kinetic Study on Cycloaddition of Allyl Radical to Acetylene

“…0196-4313/80/1019-0340$01.00/0 Thus, Nohara and Sakai (1973) found the formation of C5 cyclic compounds such as cyclopentadlene and cyclopentene to be primary products in the pyrolysis of 1,5hexadiene (diallyl). Furthermore, Sakai and Nohara (1975) reported that cyclopentene and 1-pentene were produced © in high selectivities by pyrolysis of diallyl in excess ethylene.…”

Addition reaction of allyl radical and butadiene

“…in the reactions of the allyl radical and unsaturated hydrocarbons other than butadiene. (See, for example, Sakai and Nohara (1975).) Besides, the temperature dependence of their rates of formation is similar to the dependence of C6 cyclic product formation in the thermal reaction of butadiene and 1-butene (Sakai et al, 1970).…”

“…Next, the products classified into (b), addition products of the allyl radical to butadiene, are cyclopentadiene, 1pentene, and C7 compounds such as 3-methyl-1,5-hexadiene and 1,6-heptadiene. It has been confirmed that an allyl radical adds, for example, to ethylene to form mainly cyclopentene and 1-pentene (Sakai and Nohara, 1975), to propylene to form methylcyclopentenes and hexene (Sakai , to acetylene to yield mostly cyclopentadiene (Nohara and Sakai, 1980), and to methylacetylene to produce methylcyclopentadienes (Nohara and Sakai, 1981). The scheme for the products formation, for example, in the ethylene case, is believed to be as follows:…”